#include <iostream>
#include <string>
#include <vector>
#include <algorithm>

int main() {
    std::string input;
    std::getline(std::cin, input);
    std::vector<std::string> a;
    std::string delimiter = " ";
    size_t pos = 0;
    std::string token;
    while ((pos = input.find(delimiter)) != std::string::npos) {
        token = input.substr(0, pos);
        a.push_back(token);
        input.erase(0, pos + delimiter.length());
    }
    a.push_back(input);

    std::string b;
    if (a.size() == 3) {
        for (const auto& i : a) {
            if (i == "one") {
                b += "1";
            } else if (i == "two") {
                b += "2";
            } else if (i == "three") {
                b += "3";
            } else if (i == "four") {
                b += "4";
            } else if (i == "five") {
                b += "5";
            } else if (i == "six") {
                b += "6";
            } else if (i == "seven") {
                b += "7";
            } else if (i == "eight") {
                b += "8";
            } else if (i == "nine") {
                b += "9";
            } else if (i == "zero") {
                b += "0";
            } else {
                std::cout << "Wrong input" << std::endl;
                return 1;
            }
        }
        std::vector<int> primes = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997, 1009};
        int i = 0;
        while (primes[i] < std::stoi(b)) {
            i++;
        }
        if ((std::stoi(b) - primes[i-1]) <= -(std::stoi(b) - primes[i])) {
            std::cout << primes[i-1] << std::endl;
        } else {
            std::cout << primes[i] << std::endl;
        }
    } else {
        std::cout << "Wrong input" << std::endl;
    }
    return 0;
}